Fifty women diagnosed with breast cancer planned to receive adjuvant radiotherapy, will participate in the study. About 15 minutes after receiving the daily radiation dose fraction, a cream containing an active vitamin D analogue will be applied to half of the breast with inspection of a nurse. The other half of the breast will have a standard cream applied . During the days that radiotherapy is not administered the standard cream will be applied to both halves of the breast in a case of strong reaction to radiotherapy (e.g. strong erythema, painful tenderness etc.)The adverse skin effects will be assessed according to the following criteria: